1. Field of the Invention
The present invention relates to a transformer.
2. Description of Related Art
In prior art, a transformer commonly comprise a winding frame, a first core and a second core. The winding frame has a primary winding area and a secondary winding area. The first core and the second core are set in the winding frame.
In another prior art, a transformer comprises a core, four winding wires wound together with each other around the core. U.S. Publication No. 2010/0109827 (US '827) assigned to TDK Corporation and published on May 6, 2010 discloses such a transformer. First and second terminal electrodes of the transformer are connected to each of both ends of the primary winding wire. The first terminal electrode is positioned close to the second terminal electrode. Third and fourth terminal electrodes are connected to each of both ends of the secondary winding wire. The third terminal electrode is positioned close to the fourth terminal electrode. Therefore, the core could only use low-permeability materials to avoid conduction between two close terminal electrodes. However, the low-permeability material such as nickel (Ni) is expensive. These winding structures are complex and high cost.
Hence, a transformer having a simple and low cost winding structure is desired.